[MERGE #5258 @pleath] OS#17497699: Re-enable pinning of types referenced in monomorphic property guards

Merge pull request #5258 from pleath:17497699

This was accidentally disabled in the polymorphic type guards change. Equivalent type checks will clear references to collected types, types used in monomorphic checks must be pinned at jit time.

Author: pleath

lib/Backend/Lower.cpp

@@ -7573,9 +7573,10 @@ Lowerer::GenerateCachedTypeCheck(IR::Instr *instrChk, IR::PropertySymOpnd *prope
     // as long as there are other objects with types equivalent on the properties referenced by this code. The type is kept alive until entry point
     // installation by the JIT transfer data, and after that by the equivalent type cache, so it will stay alive unless or until it gets evicted
     // from the cache.
-    if (directCheckType != nullptr)
+    if (!doEquivTypeCheck)
     {
-        PinTypeRef(directCheckType, directCheckType.t, instrChk, propertySymOpnd->m_sym->AsPropertySym()->m_propertyId);
+        Assert(monoType != nullptr);
+        PinTypeRef(monoType, monoType.t, instrChk, propertySymOpnd->m_sym->AsPropertySym()->m_propertyId);
     }
 
     return typeOpnd;